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Mario R Romano, Alessandro Stocchino, Mariantonia Ferrara, Irene Nepita, Rodolfo Repetto; Performance assessment of ultrasound vs guillotine vitrectomy probes.. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5799.
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© ARVO (1962-2015); The Authors (2016-present)
Recently, a new vitrectomy system equipped with an ultrasound vitrectomy probe (UVP) has been proposed as alternative to the guillotine VP (GVP), but no previous study assessed the fluidics of UVP and the related heat production. Aim of this study was to assess the performance of different GVP and UVP. We performed laboratory tests on 23-gauge (g) and 25g single blade GVP, 25g and 27g bi-blade GVP, and 23g UVP in the two existing port designs (large, L, and tear-drop, TD).
The experiments were performed in a transparent cubical chamber filled with the working fluids (viscoelastic artificial vitreous and balanced salt solution). To measure the volumetric flux (Q), we tracked the vertical position of a floating plastic panel placed on the free fluid surface. Using particle image velocimetry we measured velocity flow fields on different planes and at different times. From the velocity field we derived various quantities that were averaged over time and space (over a circle with 6-mm radius around the port). We changed the controlling parameters in the following ranges: ultrasound stroke (0-60 µm), vacuum (0-600 mmHg), cut rate (0-7500 cpm). Temperature was measured in water using an infrared thermal camera (FLIR i7).
We mostly focused on the flux Q and averaged acceleration (A). Both parameters increased as the vacuum grew with all VP. Q slightly decreased as cut rate (for the GVP) and the stroke (for the UVP) increased. For the GVP, A peaked for cutting frequencies in the range 4000-5000 cpm. Similarly, we found that, for the UVP, A peaked in the range 20-40 µm. GVP generally produced higher accelerations for a given flux. With the TD port, for a given flux, the acceleration was lower than with the L port. Temperature significantly increased only for strokes of 50-60 µm (≈2.5 °C after 5 min) with both UVP. The cutter head was the hottest part, but the temperature there remained close to body temperature.
Overall, UVP performed better than GVP in terms of both Q and A. Moreover, the TD UVP has better fluidics compared with the L UVP, resulting lower A for a given Q. Using UVP, temperature significantly increased only at high stroke values, remaining in a physiological range.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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